Lifting apparatus

Abstract

A lifting apparatus comprises a mobile vehicle, a platform disposed above the mobile vehicle, a single telescopic stretchable boom pivotally joined at the lower end with a pin to the mobile vehicle and at the upper end with a pin to the platform, and a hydraulic control system comprising a control circuit and a hydraulic circuit. The control circuit controls the hydraulic circuit according to detection signals given thereto from an extension detecting unit for detecting the extension of the stretchable boom and an inclination detector for detecting the inclination of the stretchable boom so that the platform is raised or lowered vertically and shifted horizontally on an elevated level through the manual control or automatic control of the control circuit or so that the platform is moved obliquely between the original position and a desired oblique position with respect to the mobile vehicle through the automatic control operation of the control circuit on the bases of recorded information relating to the oblique position. The control circuit also controls the hydraulic circuit so that the platform is always held in parallel to the upper surface of the deck of the mobile vehicle during the platform moving operation.

What is claimed is: 
     
       1. A lifting apparatus comprising: (a) a mobile vehicle;   (b) a platform disposed over said mobile vehicle;   (c) a stretchable boom pivotally joined at the lower end thereof with a pin to said mobile vehicle and at the upper end thereof with a pin to said platform, for raising or lowering said platform relative to said mobile vehicle;   said stretchable boom comprising a lowermost boom pivotally joined to said mobile vehicle with the pin, an uppermost boom pivotally joined to said platform with the pin, and a plurality of intermediate booms slidably inserted one in another in a telescopic fashion with the lowermost intermediate boom slidably inserted in said lowermost boom and said uppermost intermediate boom inserted in and fixed to said uppermost boom;   (d) an extension detecting unit for detecting the existing length, of said stretchable boom represented by the center distance between the pin pivotally joining the stretchable boom to said mobile vehicle and the pin pivotally joining said stretchable boom to said platform;   (e) an inclination detector for detecting the existing inclination of said stretchable boom;   (f) a hydraulic control system comprising a control circuit and a hydraulic circuit;   said control circuit being capable of controlling the operation of the hydraulic circuit on the basis of the detection signals given thereto from said extension detecting unit and said inclination detector so that said platform is raised or lowered vertically with respect to and directly above said mobile vehicle and so that said platform is always held in parallel to the upper surface of the deck of said mobile vehicle; and   (g) a power unit including a hydraulic pump for supplying the pressurized working fluid to said hydraulic circuit, and driving means for driving said hydraulic pump, and mounted on said mobile vehicle.   
     
     
       2. A lifting apparatus according to claim 1, wherein said hydraulic circuit comprises: (a) a tank containing the working fluid;   (b) a hydraulic pump for supplying said working fluid to said hydraulic cirucit;   (c) hydraulic clylinders for extending or contracting said stretchable boom;   (d) hydraulic cylinders for varying the inclination of said stretchable boom;   (e) hydraulic cylinders for varying the angle between said stretchable boom and said platform;   (f) a selector valve for selectively supplying said working fluid to said hydraulic cylinders and having a selector lever for selectively shifting valve position of said selector valve;   (g) solenoid valves for regulating the operation of said hydraulic cylinders; and   (h) piping properly interconnecting the components of said hydraulic circuit.   
     
     
       3. A lifting apparatus according to claim 2, wherein said solenoid valves are ON-OFF solenoid valves, and said selector valves are electromagnetic three-position selector valves. 
     
     
       4. A lifting apparatus according to claim 1, wherein said control circuit comprises: (a) an arithmetic data processing unit;   (b) a read-only memory for storing predetermined control programs and constants;   (c) a random access memory for storing control programs to be executed and variables;   (d) a digital signal input-output device;   (e) an analog-to-digital converter connected to said inclination detector;   (f) a counter connected to said extension detecting unit and to said digital input-output device;   (g) an interrupt input device which receives interrupt signals;   (h) a driving sensor electrically connected to said selector lever and to said interrupt input device, for detecting the valve position of said selector valve and for giving a signal corresponding to the valve position of said selector valve to said interrupt input device of said control circuit; and   (i) bus lines properly interconnecting the components of said control circuit.   
     
     
       5. A lifting apparatus according to claim 1, wherein said control circuit calculates the horizontal distance between the centers of the pin pivotally joining said stretchable boom to said mobile vehicle and the pin pivotally joining said stretchable boom to said platform, by an expression A=Ln·cosθ n, where Ln is the center distance between the pins corresponding to the detection signal of said extension detecting unit, and θ n is the inclination of the stretchable boom corresponding to the detection signal of said inclination detector, and then said control circuit controls said hydraulic circuit according to the detection signals of said extension detecting unit and said inclination detector so that the difference between the calculated value A and a fixed value C corresponding to the center distance between the pins pivotally joining said stretchable boom to said mobile vehicle and to said platform, respectively when said stretchable boom is fully contracted, is always smaller than a predetermined value and so that said platform is always held in parallel to the upper surface of the deck of said mobile vehicle as the same is raised or lowered vertically. 
     
     
       6. A lifting apparatus according to claim 1, wherein said extension detecting unit comprises: (a) a base fixed to said uppermost boom;   (b) a rotary shaft rotatably supported on said base;   (c) a tape fixed at one end to said rotary shaft and at the other end to said lowermost boom, and wound on said rotary shaft so as to be extended and retracted as said stretchable boom is extended and contracted, respectively;   (d) a digital encoder coupled with said rotary shaft and electrically connected to said counter of said control circuit; and   (e) a cover covering said rotary shaft and said digital encoder.   
     
     
       7. A lifting apparatus according to claim 1, wherein said inclination detector is a potensiometer. 
     
     
       8. A lifting apparatus comprising: (a) a mobile vehicle;   (b) a platform disposed over said mobile vehicle;   (c) a stretchable boom pivotally joined at the lower end thereof with a pin to said mobile vehicle and at the upper end thereof with a pin to said platform, for raising or lowering said platform relative to said mobile vehicle; said stretchable boom comprising a lowermost boom pivotally joined to said mobile vehicle with the pin, an uppermost boom pivotally joined to said platform with the pin, and a plurality of intermediate booms slidably inserted one in another in a telescopic fashion with said lowermost intermediate boom slidably inserted in said lowermost boom and said upper most intermediate boom inserted in and fixed to said uppermost boom;   (d) an extension detecting unit for detecting the existing length of said stretchable boom represented by the center distance between the pin pivotally joining said stretchable boom to said platform;   (e) an inclination detector for detecting the existing inclination of said stretchble boom;   (f) a hydraulic control system comprising a control circuit and a hydraulic circuit; and   (g) a power unit including a hydraulic pump for supplying the pressurized working fluid to said hydraulic circuit, and driving means for driving said hydraulic pump, and mounted on said mobile vehicle;   said control cirucit being capable of controlling the operation of the hydraulic circuit on the basis of the detection signals given thereto from said extension detecting unit and said inclination detector so that said platform is raised or lowered vertically with respect to and directly above said mobile vehicle, so that said platform is raised or lowered vertically in front of said mobile vehicle and so that said platform is always held in parallel to the upper surface of the deck of said mobile vehicle.   
     
     
       9. A lifting apparatus according to claim 8, wherein aid hydraulic circuit comprises: (a) a tank containing the working fluid;   (b) a hydraulic pump for supplying the working fluid to said hydraulic circuit;   (c) hydraulic cylinders for extending or contracting said stretchable boom;   (d) hydraulic cylinders for varying the inclination of said stretchable boom;   (e) hydraulic cylinders for varying the angle between th stretchable boom and said platform;   (f) a selector valve for selectively supplying the working fluid to said hydraulic cylinders, and having a selector lever for selectively shifting the valve position of said selector valve;   (g) solenoid valves for regulating the operation of said hydraulic cylinders; and   (h) piping properly interconnecting the components of said hydraulic circuit.   
     
     
       10. A lifting apparatus according to claim 9, wherein said solenoid valves are ON-OFF solenoid valves, and said selector valves are electromagnetic three-position selector valves. 
     
     
       11. A lifting apparatus according to claim 8, wherein said control circuit comprises; (a) an arithmetic data processing unit;   (b) a read-only memory for storing predetermined control programs and constants;   (c) a random access memory for storing control programs to be executed and variables;   (d) a digital signal input-output device;   (e) a digital signal output device;   (f) an analog-to-digital converter connected to said inclination detector;   (g) a counter connected to the extension detecting unit and to said digital input-output device;   (h) an interrupt input device which receives interrupt signals; a driving sensor electrically connected to said selector lever and to said interrupt input device, for detecting the valve position of said selector valve and for giving a signal corresponding to the valve position of said selector valve to the interrupt input device of said control cirucit;   (i) extension control means which gives a signal indicating that only said hydraulic cylinders for extending or contracting said stretchable boom are to be actuated to extend said stretchable boom forward to said interrupt input device; and   (j) bus lines properly interconnecting the components of said control circuit.   
     
     
       12. A lifting apparatus according to claim 8, wherein said control circuit calculates the horizontal distance between the centers of the pin pivotally joining the stretchable boom to said mobile vehicle and the pin pivotally joining said stretchable boom to said platform, by an expression A=Ln·cos θn, where Ln is the center distance between the pins corresponding to the detection signal of the extension detecting unit, and θn is the inclination of said stretchable boom corresponding to the detection signal of said inclination detector, and then said control circuit controls said hydraulic circuit according to the detection signals of said extension detecting unit and said inclination detector so that the difference between the calculated value A and a fixed value C corresponding to the center distance between the pins pivotally joining the stretchable boom to said mobile vehicle and to said platform, respectively, when said stretchable boom is fully contracted, or the difference between the calculated value A and a predetermined value C+D, where D is an optional value meeting a condition depending on the maximum center distance between the pins and a desired level to which said platform is to be raised, is always smaller than a predetermined value and so that said platform is always held in parallel to the upper surface of the deck of said mobile vehicle as the same is raised or lowered. 
     
     
       13. A lifting apparatus according to claim 8, wherein said extension detecting unit comprises: (a) a base fixed to said uppermost boom;   (b) a rotary shaft rotatably supported on said base;   (c) a tape fixed at one end to said rotary shaft and at the other end to said lowermost boom, and wound on said rotary shaft so as to be extended and retracted as said stretchable boom is extended and contracted respectively;   (d) a digital encoder coupled with said rotary shaft and electrically connected to said counter of said control circuit; and   (e) a cover covering said rotary shaft and said digital encoder.   
     
     
       14. A lifting apparatus according to claim 8, wherein said inclination detector is a potentiometer. 
     
     
       15. A lifting apparatus comprising: (a) a mobile vehicle;   (b) a platform disposed over said mobile vehicle;   (c) a stretchable boom pivotally joined at the lower end thereof with a pin to said mobile vehicle and at the upper end thereof with a pin to said platform, for raising or lowering said platform relative to said mobile vehicle; said stretchable boom comprising a lowermost boom pivotally joined to said mobile vehicle with the pin, an uppermost boom pivotally joined to said platform with the pin, and a pluraity of intermediate booms slidably inserted one in another in telescopic fashion with said lowermost intermediate boom slidably inserted in said lowermost boom and said uppermost intermediate boom inserted in and fixed to said uppermost boom;   (d) an extension detecting unit for detecting the existing length of said stretchable boom represented by the center distance between the pin pivotally joining said stretchable boom to said mobile vehicle and the pin pivotally joining the stretchable boom to said platform;   (e) an inclination detector for detecting said existing inclination of said stretchable boom;   (f) a hydraulic control system comprising a control circuit and a hydraulic circuit;   said control circuit being capable of controlling the operation of said hydraulic cirucit on the basis of said detecting signals given thereto from said extension detecting unit and said inclination detector so that said platform is raised or lowered vertically with respect to and directly above said mobile vehicle, so that said platform is shifted horizontally on an elevated level and so that said platform is always held in parallel to the upper surface of the deck of said mobile vehicle; and   (g) a power unit including a hydraulic pump for supplying the pressurized working fluid to said hydraulic circuit, and driving means for driving said hydraulic pump, and mounted on said mobile vehicle.   
     
     
       16. A lifting apparatus according to claim 15, wherein said hydraulic circuit comprises: (a) a tank containing the working fluid;   (b) a hydraulic pump for supplying the working fluid to said hydraulic circuit;   (c) hydraulic cylinders for extending or contracting said stretchable boom;   (d) hydraulic cylinders for varying the inclination of said stretchable boom;   (e) hydraulic cylinders for varying the angle between said stretchable boom and said platform;   (f) a first selector valve for selectively supplying the working fluid to said hydraulic cylinders, for vertically moving said platform, and having a first selector lever for selectively shifting the valve position of said first selector valve;   (g) a second selector valve for supplying the working fluid to said hydraulic cylinders, for horizontally moving said platform, and having a second selector lever for selectively shifting the valve position of said second selector valve;   (h) solenoid valves for regulating the operation of the hydraulic cylinders; and   (i) piping properly internconnecting the components of said hydraulic circuit.   
     
     
       17. A lifting apparatus according to claim 16, wherein said solenoid valves are ON-OFF solenoid valves, and said selector valves are electromagnetic three-position selector valves. 
     
     
       18. A lifting apparatus according to claim 15, wherein said control circuit comprises: (a) an arithmetic data processing unit;   (b) a read-only memory for storing predetermined control programs and constants;   (c) a random access memory for storing control programs to be executed and variables;   (d) a digital signal input-output device;   (e) a digital signal output device;   (f) an analog-to-digital converter connected to said inclination detector;   (g) a counter connected to said extension detecting unit and to said digital input-output device;   (h) an interrupt input device which receives interrupt signals;   (i) a first driving sensor electrically connected to said first selector lever and to said interrupt input device, for detecting the valve position of said first selector valve and for giving a signal corresponding to the valve position of said first selector valve to said interrupt input device of said control circuit;   (j) a second driving sensor electrically connected to said second selector lever and to said interrupt input device, for detecting the valve position of said second selector valve and giving a signal corresponding to the valve position of said second selector valve to said interrupt input device of said control circuit;   (k) extension control means which gives a signal indicating that only said hydraulic cylinders for extending or contracting said stretchable boom are to be actuated to said interrupt input device; and   (l) bus lines properly interconnecting the components of said control circuit.   
     
     
       19. A lifting apparatus according to claim 15, wherein first and second selector valves are interlocked mechanically to inhibit the simultaneous operation of said first and second selector valves. 
     
     
       20. A lifting apparatus according to claim 15, wherein said control circuit calculates, in raising or lowering said platform vertically with respect to and directly above said mobile vehicle, the horizontal distance between the centers of the pin pivotally joining the stretchable boom to said mobile vehicle and the pin pivotally joining the stretchable boom to said platform, by an expression: A=Ln·cos θn, where Ln is the center distance between the pins corresponding to the detection signal of said extension detecting unit, and θn is the inclination of said stretchable boom corresponding to the detection signal of said inclination detector, and then said control circuit controls said hydraulic circuit according to the detection signals of said extension detecting unit and said inclination detector so that the difference between the calculated value A and a fixed value C corresponding to the center distance between the pins pivotally joining the stretchable boom to said mobile vehicle and said platform, respectively, when said stretchable boom is fully contracted, is always smaller than a predetermined value and so that said platform is always held in parallel to the upper surface of the deck of said mobile vehicle, or calculates, in horizontally shifting said platform on an elevated level, the vertical center distance betweend the pins pivotally joining the stretchable boom to said mobile vehicle and said platform, by an expression: B=Ln·sin θn, where Ln is the center distance between the pins corresponding to the detection signal of said extension detecting unit, and θn is the inclination of said stretchable boom corresponding to the detection signal of said inclination detector, and then said control circuit controls said hydraulic cirucit so that the difference between the calculated value B and the height Ho of the elevated level is always smaller than a predetermined value and so that said platform is always held in parallel to the upper surface of the deck of said mobile vehicle. 
     
     
       21. A lifting apparatus according to claim 15, wherein said extension detecting unit comprises: (a) a base fixed to said uppermost boom;   (b) a rotary shaft rotatably supported on said base;   (c) a tape fixed at one end to said rotary shaft and at the other end to said lowermost boom, and wound on said rotary shaft so as to be extended and retacted as said stretchable boom is extended and contracted, respectively;   (d) a digital encoder coupled with said rotary shaft and electrically connected to said counter of said control circuit; and   (e) a cover covering said rotary shaft and said digital encoder.   
     
     
       22. A lifting apparatus according to claim 15, wherein, said inclination detector is a potentiometer. 
     
     
       23. A lifting apparatus comprising: (a) a mobile vehicle;   (b) a platform disposed over said mobile vehicle;   (c) a stretchable boom pivotally joined at the lower end thereof with a pin to said mobile vehicle and at the upper end thereof with a pin to said platform, for raising or lowering said platform relative to said mobile vehicle;   said stretchable boom comprising a lowermost boom pivotally joined to said mobile vehicle with the pin, an uppermost boom pivotally joined to said platform with the pin, and a pluraity of intermediate booms slidably inserted one in another in a telescopic fashion with said lowermost intemediate boom slidably inserted in said lowermost boom and said uppermost intermediate boom inserted in and fixed to said uppermost boom;   (d) an extension detecting unit for detecting the existing length of said stretchable boom represented by the center distance between the pin pivotally joining said stretchable boom to said mobile vehicle and the pin pivotally joining said stretchable boom to said platform;   (e) an inclination detector for detecting the existing inclination of said stretchable boom;   (f) a hydraulic control system comprising a control circuit and a hydraulic circuit;   (g) and a power unit including a hydraulic pump for supplying the pressurized working fluid to said hydraulic circuit, and driving means for driving said hydraulic pump, and mounted on said mobile vehicle;   said control circuit being capable of automatically moving said platform from the original position to a recorded oblique position first by vertically raising said platform from the original position to an elevated, level corresponding to the recorded oblique position secondly by horizontally shifting said platform to a horizontal position corresponding to the recorded oblique position, capable of automatically moving said platform from the recorded oblique position to the original position first by shifting said platform from the oblique position to a vertical position corresponding to the recorded to the recorded oblique position and directly above said mobile vehicle and secondly by vertically lowering said platfrorm to the original position, capable of automatically and obliquely moving said platform from the original position to the recorded oblique position by first turning said stretchable boom from the original position to a position where the inclination of said stretchable boom is the same as the inclination of said stretchable boom when the pin joining said stretchable boom to said platform is moved to the recorded oblique position and secondly by extending said stretchable boom so that the pin joining said stretchable boom to said platform reaches the recorded oblique position, capable of automatically and obliquely lowering said platform from the recorded oblique position to the original position first by fully contracting said stretchable boom and secondly turning said stretchable boom to the original position, and capable of always holding said platform in parallel to the upper surface of the deck of said mobile vehicle.   
     
     
       24. A lifting apparatus according to claim 23, wherein said hydraulic circuit comprises: (a) a tank containing the working fluid;   (b) a hydraulic pump for supplying the working fluid to said hydraulic circuit;   (c) hydraulic cylinders for extending or contracting said stretchable boom;   (d) hydraulic cylinders for varying the inclination of said stretchable boom:   (e) hydraulic cylinders for varying the angle between said stretchable boom and said platform;   (f) a first selector valve for selectively supplying the working fluid to said hydraulic cylinders, for vertically moving said platform;   (g) a second selector valve for supplying the working fluid to said hydraulic cylinders, for horizontally moving said platform;   (h) solenoid valves for regulating the operation of said hydraulic cylinders; and   (i) piping properly interconnecting the components of said hydraulic circuit.   
     
     
       25. A lifting apparatus according to claim 24, wherein said solenoid valves are ON-OFF solenoid valves, and said selector valves are electromagnetic three-position selector valves. 
     
     
       26. A lifting apparatus according to claim 23, wherein said control circuit comprises: (a) an arithmetic data processing unit;   (b) a read-only memory for storing predetermined control programs and constants;   (c) a random access memory for storing control programs to be executed and variables;   (d) a digital signal input-output device;   (e) a digital signal output device electrically connected to said solenoid valves, said first selector valve and said second selector valve to control the operation of the same;   (f) an anlalog-to-digital converter connected to said inclination detector;   (g) a counter connected to said extension detecting unit and to said digital input-output device;   (h) an interrupt device which receives interrupt signals;   (i) a control box having a control lever capable of being thrown to either one of four conrol positions, namely, an UP-position, a DOWN-position, a FORWARD-position, a BACKWARD-position and a STOP-position, electrically connected to said interrput input device;   (j) an automatic control board having a MEMORY button for storing a desired position of said platform, a MODE button for selecting the mode of operation of the hudraulic circuit an AUTOMATIC UP button for actuating said hydraulic circuit for automatic platform raising operation and an AUTOMATIC DOWN button for actuating said hydraulic circuit for automatic platform lowering operation;   (k) bus lines properly interconnecting the components of said control circuit.   
     
     
       27. A lifting apparatus according to claim 23, wherein said control circuit calculates in raising or lowering said platform vertically with respect to and directly above said mobile vehicle, the horizontal center distance between the pins pivotally joining said stretchable boom to said mobile vehicle and said platform, respectively, by an expression: A=Ln·cos θn, where Ln is the center distance between the pins corresponding to the detection signal of said extension detection unit, and θn is the inclination of said stretchable boom corresponding to the detection signal of said inclination detector, and then said control circuit controls said hydraulic circuit according to the detection signals of the extension detecting unit and said inclination detector so that the difference between the calculated value A and a fixed value C corresponding to the center distance between the pins pivotally joining said stretchable boom to said mobile vehicle and said platform, respectively, when said stretchable boom is fully contracted, is always smaller than a predetermined value and so that said platform is always held in parallel to the upper surface of the deck of said mobile vehicle; said control circuit calculates, in horizontal shifting said platform on an elevated level, the vertical center distance between the pins pivotally joining said stretchable boom to said mobile vehicle and said platform, by an expression B=Ln·sin θn, where Ln is the center distance between the pins corresponding to the detection signal of the extension detecting unit, and θn is the inclination of said stretchable boom corresponding to the detection signal of said inclination detector, and then said conrol circuit controls said hydraulic circuit so that the difference between the calculated value B and the height Ho of the elevated level is always smaller than a predetermined value and so that said platform is always held in parallel to the upper surface of the deck of said mobile vehicle, and said control circuit calculates, in obliquely raising or lowering said platform, a requisite inclination of the stretchable boom by an expression: θA=tan -1  ·{Ho/(C+lo)}, where θA is the requisite inclination, Ho is the recorded height of the oblique position, C is a fixed value corresponding to the center distance between the pins pivotally joining said stretchable boom to said mobile vehicle and said platform as said stretchable boom is fully contracted, and lo is the recorded extension of said stretchable boom from the original position, actuates said hydraulic circuit to turn said stretchable boom at the inclination θA, then calculates the necessary center distance between the pins by an expression: LA=√(C+lo) 2  +Ho 2 , and then controls said hydraulic circuit to increase the center distance between the pins to the calculated center distance LA and to hold the platform in parallel to the upper surface of the deck of said mobile vehicle during the movement of said platform.   
     
     
       28. A lifting apparatus according to claim 23, wherein said extension detecting unit comprises: (a) a base fixed to the uppermost boom;   (b) a rotary shaft rotatably supported on said base;   (c) a tape fixed at one end to said rotary shaft and at the other end to said lowermost boom, and wound on said rotary shaft so as to be extended and retracted as said stretchable boom is extended and contracted, respectively;   (d) a digital encoder coupled with said rotary shaft and electrically connected to said counter of said control circuit; and   (e) a cover covering said rotary shaft and said digital encoder.   
     
     
       29. A lifting apparatus according to claim 23, wherein said inclination detector is a potentiometer.